Dissolvable downhole frac tool having a single slip

ABSTRACT

A downhole plug for use in completion operations within the casing of an oil well is disclosed. The settable downhole tool has a mandrel, a wedge, a seal, load ring, ratchet ring, a bottom shoe, and a ball seat. In addition, the downhole tool contains only a single slip engaging the mandrel, the slip comprised of numerous panels with multiple buttons thereon. During setting of the downhole tool, the single slip engages the wedge and is forced outward to engage the casing so as to hold the downhole tool in place during subsequent operations, including, for example, fracing.

This is a utility application that elms priority and the benefit of U.S. Provisional Application 62/519,350, filed Jun. 14, 2017.

FIELD OF THE INVENTION

Downhole tools, more specifically, downhole tools that are dissolvable in a downhole fluid, and/or are shorter in overall length than typical, and/or may have only a single slip of novel construction and dimensions.

BACKGROUND OF THE INVENTION

Downhole tools may be used in completion of oil and gas wells, in one example, for fracing operations by isolating the formations downhole to be treated as, for example, by fracing. These downhole tools may be interventionless, meaning they may be dissolvable in downhole fluids. Downhole fluids may be naturally occurring, or may be fluids added at the wellhead during completion, or fluids modified by adding chemicals at the wellhead to the natural downhole fluids or introduced fluids.

Dimensionally, most downhole tools have an overall length of about 13″ to 32″ long and weigh in the range of about 6 to 12 pounds. Reducing dimensions, such as weight and overall length, and mandrel wall thickness will create a lighter, easier handling, smaller tool. However, this is difficult, especially when balancing other goals, such as degradability strength). It is a challenge to make a tool which achieves degradability while also being light and compact. Nonetheless, disclosed herein are embodiments of tools that achieve, in an interventionless tool, useful size, weight, and other design parameters.

SUMMARY OF THE INVENTION

This application incorporates by reference the following: US Publication No. 2017/0067312, as well as US Publication No. 2017/0030161; U.S. patent application Ser. No. 13/969,066, filed Aug. 16, 2013, which is a continuation-in-part of U.S. patent application Ser. No. 13/895,707, filed May 23, 2013; U.S. patent application Ser. No. 13/894,649, filed May 15, 2013, which is a continuation of and claims priority to U.S. patent application Ser. No. 13/843,051, filed Mar. 15, 2013; and which claims the benefit of U.S. Provisional Application 61/648,749, filed May 18, 2012; U.S. Provisional Application 61/738,519, filed Dec. 18, 2012. All of the foregoing and US Patent Publication No. 2010/0155050, published Jun. 24, 2010, which is now U.S. patent application Ser. No. 12/317,497, filed Dec. 23, 2008, are incorporated herein by reference. U.S. Pat. No. 6,951,956 is also incorporated herein by reference. All of the foregoing patents, applications, and publications are incorporated herein by reference.

A downhole tool or plug is provided, in some embodiments, comprising: a mandrel, a bottom shoe engaging the mandrel, a single slip engaging the mandrel, a single wedge engaging the mandrel, an elastomer engaging the mandrel, a load ring engaging the mandrel; and a ratchet ring engaging the mandrel. One or more of the foregoing elements may be comprised of at least a first degradable material and, in some embodiments, a second degradable material. The first degradable material may be a metal, such as an aluminum, magnesium or zinc alloy. The second degradable material may be a polymer acid, such as polyglycolic or polylactic acid. A frac ball may be provided and either the removed end of the mandrel or the bottom shoe may be configured to receive the frac ball. The frac ball may be comprised of a degradable polymer acid or other degradable material such as a magnesium alloy. The slip may include multiple buttons. The multiple buttons may include a first set and a second set, the first set inclined in a first direction and a second set inclined in a second direction, thus holding the tool bi-directionally in the casing from moving either up or down. Bi-directional buttons may be in one or more slip elements. The elastomer may be degradable and comprised of a polyglycolic acid (“PGA”), a polylactic acid (“PLA”) or other degradable polymers or materials. The downhole tool may further include a tablet for Increasing the rate of dissolution of the one or more degradable elements.

In some embodiments, the plugs disclosed herein are “interventionless” if they do not have to be milled or drilled or retrieved from the well so completion can continue after their function is completed, but rather can be left in the well where they degrade, disintegrate or dissolve to the same effect. “Degrade” and “dissolve” are used interchangeably into the same effect herein. Interventionless downhole plugs may save time and expense in well completion and workover processes, including fracing and/or acid completions. In some embodiments, settable downhole tools combine one or more degradable polymeric or polymer acid elements with one or more degradable metallic elements to produce a tool which sets, and sufficiently degrades to no longer interfere with fluid flow through the casing without drilling out. In some embodiments, the degradable elements and the composition thereof are disclosed in U.S. patent applications: Ser. No. 13/893,160, filed May 13, 2013; Ser. No. 14/132,608, filed Dec. 18, 2013; and Ser. No. 14/677,242, filed Apr. 2, 2015, all incorporated herein by reference.

In one embodiment, the degradable polymer acid elements are non-composite elements and the degradable metallic elements are non-iron. Composite downhole tool elements tend to typically include a woven fabric and resin, such as a fiberglass. Unless otherwise indicated herein, “metal” includes in some embodiments pure metal and in other embodiments metal alloys. In some embodiments, the non-iron, degradable metallic elements may be aluminum (meaning pure aluminum or aluminum alloy) or magnesium (meaning pure magnesium or magnesium alloy) combined with the degradable non-metallic elements. In some embodiments, the degradable metallic elements include a bottom sub, a shear sub and/or slips and the non-metallic polymer acid degradable elements may include a mandrel. In some embodiments, the slip or slips include a body with cast iron buttons or other hard metal buttons, the body being comprised of a degradable, non-iron metallic.

The degradable, settable downhole tool is provided for engaging a casing at a rated setting strength, the casing containing a downhole fluid, typically an aqueous completion fluid, which may be freshwater or contain a salt of various concentrations, most typically about 2% NaCl or other chloride. In one embodiment, the tool has a degradable mandrel comprising at least in part, a degradable metal or solid high molecular weight acid polymer which is strong and hard enough to function as a mandrel and degradable enough in the downhole fluid to degrade enough so completion operations can continue without drilling out the mandrel and the degradation releases an acid into the downhole fluid, which changes the chemistry of the local downhole fluid to increase the rate of dissolution of at least some other parts of the tool.

For example, the polymer acid solid may be a pH neutral, high molecular weight PLA, PGA, PHA or any polymerized acid which, in some embodiments, is both (1) strong and hard enough to function as a downhole tool element, and (2) hydrolyzes in the aqueous drilling fluid to release enough acid with a low enough pH quickly enough into the local downhole fluid immediately adjacent the tool's metal elements to appreciably accelerate degradation of the tool's metal elements. For example, degradation of a solid high molecular weight polyglycolic acid in an aqueous downhole fluid solution may release glycolic acid and degradation of a solid high molecular weight polylactic acid polymer in an aqueous downhole fluid may release a lactic acid. Other polymers that degrade in an aqueous solution and release acid are found in U.S. Pat. No. 7,353,879, incorporated herein by reference. In some embodiments, the solid acid polymer elements of the tool react by hydrolysis in the aqueous downhole fluid, releasing acids into the downhole fluid as reaction products. The released acid in the local downhole fluid immediately adjacent to the tool's metallic elements speeds degradation of the nearby tool metallic elements, such as load rings and/or slips and/or cones, which may be made of ferric or non-ferric metals or any acid degradable material. In one embodiment some of the mandrel, slip, wedge, seal, load ring, ratchet ring, and bottom shoe are polymer acid elements comprised of one or more degradable polymer acids and some of the mandrel, slip, wedge, seal, load ring, ratchet ring and bottom shoe are metallic elements comprised of metals or metal alloys, the polymer acid elements being degradable in the well's downhole fluid to produce degradation products which will sufficiently reduce the pH of the downhole fluid adjacent the metallic elements to appreciably accelerate the degradation rate of the metallic elements relative to the degradation rate of the metallic elements without the adjacent polymer acid elements degradation products so the plug releases from the casing in 80% of the time needed for a similar plug without such degradable polymer elements producing such degradation products to release from the casing

The degradable metal alloy, in one embodiment, is a degradable zinc alloy. The degradable metal alloy, in one embodiment, is a magnesium alloy as described in U.S. Patent Application No. 2016/0024619, incorporated herein by reference. The degradable metal alloy is degradable in the presence of water and chlorides with a pH of less than 7. The degradable metal alloy, in one embodiment, comprises one or more of the following: one slip, a bottom cone, a bottom shoe and a load ring. The polymer, in one embodiment, is degradable PGA or PLA and may comprise a cone and/or a bottom shoe or sub. The central elastomer may be degradable or dissolvable in aqueous downhole fluid. The slip, in one embodiment, may have heat treated ductile iron buttons or heat treated powder metal buttons.

In one embodiment, a bottom cone and a bottom shoe, all the foregoing elements and the mandrel may at least partly comprise a poly acid plastic. The central elastomer may be a dissolvable rubber or plastic. The degradable metal of any metal part may be as disclosed in US 2015/0240337; US 2015/0299838; or US 2015/0239795, all incorporated herein by reference.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial cutaway of a side view of an embodiment of Applicant's degradable downhole tool.

FIGS. 2A, 2B1. 2B2 illustrate one embodiment of a slip for use with Applicant's downhole tool. FIGS. 2C and 2D are views of another slip for use in Applicant's dissolvable downhole tool.

FIG. 3 is an alternate embodiment of Applicant's dissolvable downhole tool.

FIG. 4 is an alternate embodiment of Applicant's dissolvable downhole tool.

FIGS. 4A and 4B are alternate embodiments of a wedge for use with Applicant's downhole tool.

FIG. 5 is an embodiment of FIG. 4 in a set position.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 illustrates one embodiment of Applicant's downhole tool 10 with a number of novel features and functional advantages. Downhole tool 10 is intended to be used in completion of oil and gas wells and, in some embodiments, for isolating a zone to be fraced. Downhole tool 10 comprises a cylindrical, thin walled and short mandrel 12 that has a bore 32 therethrough for selectively allowing the passage, when in a set position of a fluid therethrough, as set forth in more detail below. Coupled to mandrel 12 is seen bottom shoe 14, which may be engaged, as by threads or other means, to the lower end of mandrel 12 and includes a bottom shoe bore 38 therethrough, bottom shoe bore 38 being in fluid communication with mandrel bore 32. Bottom shoe 14 may include walls defining bottom shoe seat 40 for receiving a spherical ball 30 (may be dropped in or run in with the tool), such as a frac ball, thereon. In an alternate embodiment, the mandrel 12 may include a ball seat 42 for receiving ball 30 thereon (see FIG. 3), in either case receipt of the ball will have the effect of sealing bores 32/38 selectively for preventing the passage of fluid downhole through tool 10 (left to right as seen in FIG. 1). O-ring 28 may be captured between the outer wall of the mandrel at the lower end of mandrel 12 and the inner wall of bottom shoe 14, which may include a cutout 14 a, seen in FIG. 1.

FIG. 1 also illustrates a number of elements received about the cylindrical outer surface 12 a of mandrel 12. These include: a single slip having buttons 34 thereon, a single wedge 18, a sealing or packing member 20 that may comprise one or more parts, a load ring 22, and a ratchet ring 24. A washer 26 may also be provided.

Generally, the setting of tool 10 may be seen in FIG. 3, where elements 12, 18, 30, 22, and 24 are compressed by a standard setting tool 44, such as a BK20 (Baker Hughes 20) (or a 358 GO Compact) setting its sleeve end 48 against load ring 22 or washer 26 as seen in FIG. 3, and applying an upward (to the left in FIG. 3) force on adaptor 46 of setting tool 44. The compression creates an upward force (to the left as seen in FIG. 3), from bottom shoe 14 to the lower surface of slip 16. Wedge 18 forces slip 16 outward as slip 16 rides up on wedge 18 or cone and breaks at grooves 16 a. Compression during setting causes the mandrel (upper walls with ratchet ridges on the outer surface) to ride up on the ratcheted inner walls of ratchet ring 24 and cause elastomer 20 to bulge out to fluidly seal against the inner walls of the casing. Compressive force generated during setting on seal 20 creates a fluid seal against the inner wall of the casing, and a grip by buttons 34 pressing into the inner wall of the casing (the buttons being harder than the casing). Further compression after setting results in adaptor 46 shearing away from the mandrel at shear screws 50. Longitudinal axis LA is indicated by the view line separation shown by the lead line in FIG. 1.

Turning now to the structure of bottom shoe 14, it is seen to have, in one embodiment, tapered walls 14 c defining a nose thereof, to facilitate moving plug 10 downhole and grooves 14 e, which may form an X-shape at the removed end of the tapered walls, so if a ball from below plug 10 comes up from below and strikes bottom shoe 14, fluid may still pass around the ball and through plug 10. Threaded walls 14 b are designed to engage threaded walls on the lower end of the mandrel. O-ring 28 held in bottom shoe ring cutout 14 a seals the bottom shoe 14/mandrel 12 interface. Any of the elements illustrated in FIG. 1 may be made of a degradable material and, in some embodiments, may be made of a degradable metal or degradable polymer acid. In any embodiment, bottom shoe 14 or any other structural element of the tool may be made of a degradable metal, such as degradable magnesium or other degradable magnesium alloy known and used in the art. Any structural element may be made of a degradable polymer, such as a polymer acid. Two exemplary such polymer acids are polyglycolic acid (PGA) and polylactic acid (PLA). In some embodiments, some elements are degradable metals and others are degradable polymers. In other embodiments, other combinations of elements are degradable metals and degradable polymers.

In the embodiment of FIG. 1, slip 16 is a single slip having multiple panels 17 a, 17 b, 17 c, etc. The slip's body or panels do not need to be as shown in the figures, but may be size, shape, connected to each other or otherwise held to the mandrel in ways known in the art. In one embodiment, a single slip is comprised of panels, at least some panels having upward buttons for holding the frac plug within the casing against downward pressure, the upward buttons having an upward face inclined upwards and a lower face generally perpendicular to the slip, and at least some panels have downward buttons for holding the frac plug within the casing against upward pressure, and the downward buttons have a downward face inclined downward and an upper face generally perpendicular to the slip. The FIG. 1 embodiment downhole tool 10 does not have two slips, as is typical in downhole tools—one slip above an elastomer and one slip below the elastomer. This embodiment has only one slip below or downhole from the elastomeric sealing or packing member 20, along with a single cone or wedge 18. Applicant has tested such a configuration in 5½″ casing 10,000 psi (4.30 inch) successfully, with slip 16 as indicated in FIG. 1 and FIGS. 2A-2D. In some embodiments, slip 16 may have multiple circumferential rows of buttons 34 and, in some cases, as in FIGS. 2A and 2B, a first button set 34 a and a second button set 34 b on the outer surface of slip panels 17 a-c, button set 34 a being canted or inclined down in an uphole direction, and button set 34 b, typically smaller in number (see FIGS. 2A, 2B1, 2B2), with buttons inclined opposite those of first set 34 a, that is, having a downhole tilt. FIGS. 2A, 2B1, and 2B2 illustrate an embodiment of single slip 16 having first button set 34 a and second button set 34 b. The embodiment of slip 16 in FIGS. 1, 2C, and 2D has buttons inclined so the leading edge of the buttons are lower and less steeply sloped than the trailing edge. The buttons of first button set 34 a with the inclination shown more easily gouge into the inner walls of the casing (moving right to left as seen in FIGS. 2C and 2D) during the setting process due to their inclination in the upper direction of their axial movement, and firmly hold the tool against downward movement (moving left to right) due to the button's steeper wall in that direction. Buttons 34 b of the second button set, of which there may be fewer than of the first button set, will tend to jam post-set against force pushing the set tool uphole from below. Typically, when the ball is seated during a frac operation most of the pressure is downward on the tool, pushing the tool downward or downhole through pressure on the ball and seat. This button arrangement provides bi-directional resistance to movement of the tool in the casing with a single slip.

Embodiments of such a slip are shown in FIGS. 2A, 2B1, 2B2, 2C, and 2D. The slip body may be longer to accommodate an additional row or rows of buttons 34, such as, in one embodiment, a slip with a body about 3″ to about 7″ long. In one embodiment, buttons 34 b of the second set may be staggered with respect to buttons 34 a of the first set, both longitudinally spaced apart and the buttons of the second set laterally spaced apart from the first set of buttons, so the second set of buttons do not ride in the same inner casing grooves created by first buttons 34 a so they can better dig into and hold in the inner casing. In one embodiment, both buttons 34 a and 34 b are in at least one or more panels 17 a, 17 b, 17 c, etc.

In one embodiment, ball seat 42 may be on an upper shoulder of a lower portion of mandrel 12 which lower mandrel 43 is thicker than the upper mandrel 45 as shown in FIG. 3. In another embodiment, ball seat 42 protrudes from a mandrel 12 inner wall which is otherwise of generally constant thickness. This structure enables use of bottom shoe 15 which does not need to hold frac ball 30 in tool 10 against downward fracing pressures. Thus, bottom shoe 15 may have a size and structure and be comprised of material which would be unable to hold frac ball 30 against downward fracing pressures if it were used as bottom 14 shoe of FIG. 1 is used in FIG. 1 with mandrel 14 of FIG. 1. This provides advantageous design flexibility, such as enabling bottom shoe 15 to be smaller than bottom shoe 14 and made of materials which have less tensile strength than bottom shoe 14 shown in FIG. 1. Bottom shoe 15 may degrade to not interfere with further completion operations in the downhole fluid more quickly than bottom shoe 14.

In one embodiment, the mandrel overall length may usefully be in the range of about 15 to about 26 inches and the plug in the range of about 16 to about 27 inches. The mandrel wall thickness may be in the range of about 1.50 to about 0.75 inches, and preferably less than of about 1 inch. The O.A. length of the downhole tool in typical use may be between about 10 and 16 inches and the length of the plug in the range of about 11 to about 17 inches. A preferable mandrel length is less than about 12 inches, the length of the plug being less than about 13 inches. A most preferable mandrel length is less than about 11 inches, the plug being less than about 12 inches.

In one embodiment, the thickness of mandrel 12 of FIG. 1 is less than the thickness of a typical frac plug mandrel wall in a typical frac plug which holds its frac ball at its upper end and less than the thickness of a similar mandrel 12 of a similar frac plug holding its frac ball at its upper end. Mandrel 12 and mandrel 45 shown in FIGS. 1 and 3 may have thinner walls and be shorter than typical frac plug mandrels. The plug of FIG. 3 has its ball seat on a mandrel shoulder located on an inner wall of the mandrel and above the bottom shoe, and at least some of the mandrel wall above the mandrel shoulder is thinner than the mandrel wall below the mandrel shoulder. In one embodiment, the mandrel's wall thickness above the ball seat is less than about 1.5 inches. It is believed that seating the frac ball at the bottom of the mandrel rather than at the top of the mandrel enables a plug to hold more downward downhole fluid pressure, more downhole fluid psi. It is believed that a relatively thin wall mandrel flexes outward, when the ball is at the bottom end of the mandrel (either on the bottom shoe or on a seat on the lower end of the mandrel) when downhole fluid pressure is applied from above the tool. It is believed the outward pressure of the downhole fluid against a relatively thin mandrel 12 or mandrel 45 is partly resisted by the casing's resisting force, transmitted by tool elements, such as its slip, wedges, load ring, and elastomer between the outer walls of the mandrel and the inner walls of the casing. A mandrel which is thinner than typical mandrels requires less material and is lighter than typical mandrels. A mandrel which is thinner than typical mandrels and may be comprised of degradable materials may degrade to not interfere with further completion operations more quickly than a similar, thicker mandrel.

Turning to FIG. 1, it is seen that single wedge 18 has sloped slip engaging walls 18 a and sloped packing member or intrusion ring engaging walls 18 b. Under compression, cone or wedge 18 performs as is known in the art to cause a radially outward force on slip 16 and cause compression of sealing member 20, boring it outward. Wedge 18 may be made from any degradable material, including a degradable polymer acid, or a degradable metal, such as a degradable aluminum alloy or magnesium alloy. Wedge 18 seen in FIGS. 3, 4A, and 4B is seen to have flex grooves 18 c to help when sections 52 a of backup rings 52 flex or move outward during the setting of the tool.

FIG. 1 also illustrates use of a tablet 36 made of any material that will interact or dissolve in a downhole fluid and act to speed up dissolution. In one embodiment, table 36 may be a salt, such as NaCl or KCl to increase the salinity of a downhole fluid to increase dissolution of the degradable parts of the tool and, in another embodiment, it may change the pH, such as increase the pH to increase the acidity and improve dissolution. The tablet may be run in with ball 30, may be introduced later or may be physically attached to the tool, such as in the interior of the mandrel, by adhesives or any other means for run in with the tool. Extra elements other than tablets which are comprised of salts or degradable parts which produced acid upon degradation, or both, may be usefully used. Such extra elements may be tablets, capsules, pouches comprised of degradable containers and the like. Degradation or dissolution of the extra elements within the mandrel's cavity creates a local downhole fluid environment which is more salty or more acidic and thus speeds degradation of plug elements which degrade more quickly and salty or acidic environments. Additional extra elements can be added as needed to speed the plug's degradation as desired.

In one embodiment, an extra element is run into the well with the plug and is degradable in the downhole fluid to produce degradation products which will sufficiently reduce the pH of the downhole fluid adjacent the metallic elements to appreciably accelerate the degradation rate of the metallic elements relative to the rate of degradation of the metallic elements without the polymer acid elements degradation products so the plug releases from the casing at least 20% faster than a similar plug without such extra degradable element producing such degradation products. In another embodiment, the extra element is or dissolvable in the downhole fluid to produce a salty solution which will sufficiently increase the salinity of the downhole fluid adjacent the metallic elements to appreciably accelerate the degradation rate of the metallic elements relative to the rate of degradation of the metallic elements without the salty elements salty dissolution products so the plug releases from the casing at least 20% faster than a similar plug without the extra element producing such salty dissolution products. In another embodiment, the extra elements produce both acid and saline solution as degradation and dissolution products. The number of extra elements used can be selected to control the degradation rate of the metallic elements and the speed of the plug releasing from the casing. In appropriate environments and with appropriate plugs, the use of such extra elements may decrease the time needed for the plug to release from the casing by 10% to 50%, a preferred range being from 20% to 30%.

Sealing or packing member 20 may be made from degradable materials such as are known in the art, including polyglycolic acid and polylactic acid which degrade to produce acid reaction products.

Load ring 22 has a general structure and function of load rings as known in the art and may be made from any degradable material and, in a preferred embodiment, a degradable polymer acid or a degradable metal. Ratchet ring 24 and washer 26, in one embodiment, may have, generally, the structure and function as set forth in the prior art. In one embodiment, they may be made from a degradable material, including a degradable acid or a degradable polymer acid.

FIG. 3 is an alternate embodiment of Applicant's dissolvable downhole tool. In this embodiment, packing member 20 may have cutouts 20 a, which function to use the axial compressive force to push the elastomer out toward and against the inner wall of the casing. FIG. 3 also includes multiple backup rings 52 having sections 52 a separated by grooves 52 c, which may be comprised of a dissolvable material, such as dissolvable aluminum or magnesium and function as anti-extrusion rings. Moreover, in this embodiment, the backup rings are two or more and located below the packing member and angled uphole. In other embodiments, there may be only one backup ring, or three or more. In other embodiments, backup rings may be on the uphole side of the packing member or both sides. Furthermore, it is seen that the lower end of mandrel 12 is configured to receive ball 30 thereon, rather than bottom shoe 14 as seen in FIG. 1.

Below is a table showing some ranges for use with Applicant's tool.

DIMENSIONS TABLE (all approximate) PREFERRED RANGE RANGE NOMINAL Mandrel Wall thickness 1.50″ to 0.4″    1″-0.5″ ⅜″ I.D. 1.00″-4.00″ 2.00″-3.00″  .75/1.25 (above/below ball) O.D. 2.00″-5.00″ 3.00″-4.00″ 2.00/1.50 (above/below ball) Length O.A.  9″ to 16″ 10″-15″ 10.75″ Inner bore .05″-3.5″ 1.5″-2.5″ 2.00″ Slip Body I.D. 1″-5″ 2″-3″ 2.770″ O.D. (buttons)  2″-12″ 4″-8″ 4.625″ O.D. (body only) 2″-6″ 2″-5″ 4.13″ Length 3″-7″ 3″-5″ 3.28″ Tool Length O.A.  9″ to 26″ 11″-13″ 11.14″

FIG. 4 (preset) and FIG. 5 (set) is an alternate embodiment of Applicant's downhole tool. The FIG. 4 slip 16 is longer than the slip of FIG. 1, and bottom shoe 14 is configured with uphole inclined walls 14 d such that, during setting, wedge 18 and the bottom shoe 14 contribute to radially expansive force on slip 16. The added length on slip 16 allows the addition of or makes it easier to add additional buttons, for bi-directionality.

The present invention is adapted to attain the ends and advantages mentioned as well as those that are inherent therein. The embodiments disclosed above are illustrative only, as the present invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. No limitations are intended to limit the details of construction or design shown, other than as described in the claims below. The illustrative embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the present invention.

The terminology used herein is for the purpose of describing particular implementations only and is not intended to be limiting. The singular form “a”, “an”, and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises” and/or “comprising,” when used in the this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups therefore. Compositions and methods described in terms of “comprising,” “containing,” or “including” various components or steps, can also “consist essentially of or “consist of the various components and steps.

Whenever a numerical range with a lower limit and an upper limit is disclosed, any number and any included range falling within the range is specifically disclosed. Every range of values (of the form, “from about a to about b,” or, equivalently, “from approximately a to b,” or, equivalently, “from approximately a to b”) disclosed herein is to be understood to set forth every number and range encompassed within the broader range of values. The terms in the claims have their plain, ordinary meaning unless otherwise explicitly and clearly defined by the patentee. If there is any conflict in the usages of a word or term in this specification and one or more patent(s) or other documents that may be incorporated herein by reference, the definitions that are consistent with this specification should be adopted.

The corresponding structure, materials, acts, and equivalents of all means or steps plus function elements in the claims below are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description is presented for the purposes of illustration and description, but is not intended to be exhaustive or limited to the implementations in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the disclosure. The implementations were chosen and described in order to explain the principles of the disclosure and the practical application and to enable others or ordinary skill in the art to understand the disclosure for various implementations with various modifications as are suited to the particular use contemplated. Those skilled in the art will readily recognize that a variety of additions, deletions, modifications, and substitutions may be made to these implementations. Thus, the scope of the protected subject matter should be judged based on the following claims, which may capture one or more concepts of one or more implementations.

Although the invention has been described with reference to a specific embodiment, this description is not meant to be construed in a limiting sense. On the contrary, various modifications of the disclosed embodiments will become apparent to those skilled in the art upon reference to the description of the invention. It is therefore contemplated that the appended claims will cover such modifications, alternatives, and equivalents that fall within the true spirit and scope of the invention. 

1. A downhole plug for use in completion operations within a casing in a hydrocarbon well, the plug being settable by a setting tool within the casing to isolate an upper zone above the plug from a lower zone below the plug, comprising: a mandrel having a at overall length less than about 26 inches; a single slip engaging the mandrel, the slip comprised of panels, at least some panels having upward buttons for holding the frac plug within the casing against downward pressure, the upward buttons having an upward face inclined upwards and a lower face generally perpendicular to the slip, and at least some panels having downward buttons for holding the frac plug within the casing against upward pressure, the downward buttons having a downward face inclined downward and an upper face generally perpendicular to the slip; a wedge engaging the mandrel and the slip for expanding the slip against the casing; a seal engaging the mandrel for sealing the plug against the casing; a load ring engaging the mandrel and the seal for axially moving on the mandrel to axially compress the seal to expand the seal radially against the casing; a ratchet ring engaging the mandrel and the load ring for axially moving downward on the mandrel and holding the load ring from upward movement on the mandrel; a bottom shoe engaging the lower end of the mandrel for holding the wedge against downward movement on the mandrel; and a ball seat engaging the mandrel or the bottom shoe for holding a frac ball; wherein the plug has an overall length of less than about 28 inches and is useful in completion operations within the casing in the hydrocarbon well, the plug being settable by a setting tool within the casing to isolate an upper zone above the plug from a lower zone below the plug.
 2. The plug of claim 1, wherein the mandrel's overall length is less than about 16 inches and the overall length of the plug is less than about 18 inches.
 3. The plug of claim 1, wherein the mandrel's overall length is less than about 11 inches and the overall length of the plug is less than about 12 inches.
 4. The plug of claim 1, wherein at least some of the upward buttons and some of the downward buttons are on the same panel or panels, and such panels with both upward buttons and downward buttons provide resistance to both upward movement and downward movement of the plug in the casing.
 5. The plug of claim 1, wherein the ball seat is on a mandrel shoulder located on an inner wall of the mandrel and above the bottom shoe, and at least some of an upper mandrel wall above the ball seat is thinner than a lower mandrel wall below the ball seat.
 6. The plug of claim 5, wherein the upper mandrel's wall thickness above the ball seat is less than about 1.5 inches.
 7. The plug of claim 5, wherein the upper mandrel's wall thickness above the ball seat is less than about 1 inch.
 8. The plug of claim 1, wherein some of the mandrel, slip, wedge, seal, load ring, ratchet ring, and bottom shoe are polymer acid elements comprised of one or more degradable polymer acids and some of the mandrel, slip, wedge, seal, load ring, ratchet ring and bottom shoe are metallic elements comprised of metals or metal alloys, the polymer acid elements being degradable in the well's downhole fluid to produce degradation products which will sufficiently reduce the pH of the downhole fluid adjacent the metallic elements to appreciably accelerate the degradation rate of the metallic elements relative to the degradation rate of the metallic elements without the adjacent polymer acid elements degradation products so the plug releases from the casing in 80% of the time needed for a similar plug without such degradable polymer elements producing such degradation products to release from the casing.
 9. The plug of claim 1, wherein some of the mandrel, slip, wedge, seal, load ring, ratchet ring, and bottom shoe are polymer acid elements comprised of one or more degradable polymer acids and some of the mandrel, slip, wedge, seal, load ring, ratchet ring and bottom shoe are metallic elements comprised of metals or metal alloys, the polymer acid elements being degradable in the well's downhole fluid to produce degradation products which will sufficiently reduce the pH of the downhole fluid adjacent the metallic elements to appreciably accelerate the degradation rate of the metallic elements relative to the degradation rate of the metallic elements without the adjacent polymer acid elements degradation products so the plug releases from the casing in 50% of the time needed for a similar plug without such degradable polymer elements producing such degradation products to release from the casing.
 10. The plug of claim 1, further including an extra degradable element which is run into the well with the plug and is degradable in the downhole fluid to produce degradation products which will sufficiently reduce the pH of the downhole fluid adjacent the metallic elements to appreciably accelerate the degradation rate of the metallic elements relative to the rate of degradation of the metallic elements without the degradation products, so the plug releases from the casing in 50% of the time needed for a similar plug without such extra degradable element producing such degradation products.
 11. The plug of claim 1, further including an extra degradable element which is run into the well with the plug and is degradable in the downhole fluid to produce degradation products which will sufficiently increase the salinity of the downhole fluid adjacent the metallic elements to appreciably accelerate the degradation rate of the metallic elements relative to the rate of degradation of the metallic elements without the degradation products, so the plug releases from the casing in 50% of the time needed for a similar plug without such extra degradable element producing such degradation products.
 12. The plug of claim 5, wherein the extra degradable element is a tablet or capsule within the cavity of the mandrel.
 13. A downhole plug for use in completion operations within a casing in a hydrocarbon well, the plug being settable by a setting tool within the casing to isolate an upper zone above the plug from a lower zone below the plug, comprising: a mandrel having a mandrel overall length of less than about 12 inches; a single slip engaging the mandrel, the slip comprised of panels, at least some panels having upward buttons for holding the frac plug within the casing against downward pressure, the upward buttons having an upward face inclined upwards and a lower face generally perpendicular to the slip, and at least some panels having downward buttons for holding the frac plug within the casing against upward pressure, the downward buttons having a downward face inclined downward and an upper face generally perpendicular to the slip, and wherein at least some of the upward buttons and some of the downward buttons are on the same panel or panels, panels with both upward buttons and downward buttons providing resistance to both upward movement and downward movement of the plug in the casing; a wedge engaging the mandrel and the slip for expanding the slip against the casing; a seal engaging the mandrel for sealing the plug against the casing; a load ring engaging the mandrel and the seal for axially moving on the mandrel to axially compress the seal to expand the seal radially against the casing; a ratchet ring engaging the mandrel and the load ring for axially moving downward on the mandrel and holding the load ring from upward movement on the mandrel; a bottom shoe engaging the lower end of the mandrel for holding the wedge against downward movement on the mandrel; a ball seat for holding a frac ball, the ball seat being on a mandrel shoulder located on an inner wall of the mandrel and above the bottom shoe, and at least some of the mandrel wall above the mandrel shoulder is thinner than the mandrel wall below the mandrel shoulder; and some of the mandrel, slip, wedge, seal, load ring, ratchet ring, and bottom shoe are polymer acid elements comprised of one or more degradable polymer acids and some of the mandrel, slip, wedge, seal, load ring, ratchet ring and bottom shoe are metallic elements comprised of metals or metal alloys, the polymer acid elements being degradable in the well's downhole fluid to produce degradation products which will sufficiently reduce the pH of the downhole fluid adjacent the metallic elements to appreciably accelerate the degradation rate of the metallic elements relative to the degradation rate of the metallic elements without the adjacent polymer acid elements degradation products so the plug releases from the casing in 80% of the time needed for a similar plug without such degradable polymer elements producing such degradation products to release from the casing; wherein the plug has an overall length of less than about 13 inches and is useful in completion operations within the casing in the hydrocarbon well, the plug being settable by a setting tool within the casing to isolate an upper zone above the plug from a lower zone below the plug.
 14. The plug of claim 10, wherein the upper mandrel's wall thickness above the ball seat is less than about 1 inch. 